text:
How to keep the centerline on upwind / departure leg?
I'm a student pilot training with C172. The area usually do not have strong winds, but when there's ~5kts crosswind component, it's difficult for me to keep the runway centerline after taking off.
I saw an advice to see a reference point in distance like a specific point of clouds and trying to follow it, but I'm still drifting towards downwind. What references do you use to keep the centerline in a departure leg / upwind?

This is a very common problem with student pilots, and to some  extent comes (like most things) with practice and experience. That said there are some visual guides you can use - sounds like you've been told about them, and some more analytical planned things you can use.
What you could do is basically the same as when you're on final; namely crab slightly into the wind. To calculate the amount you can use the typical "Max Drift" calculation (based on a simple rule of thumb 1:60 rule) and then estimate based on the crosswind component.
For example:

You're taking off from runway 26, and your TAS is 80Kts. The wind is 290/12

$ \text{Max Drift} = \frac {60} {80} \times 12 = 9 $
Then calculate the wind correction by a simple estimate based on crosswind component

15 degrees off = apply quarter
30 degrees off = apply half
45 degrees off = apply three quarters
60 degrees or more = apply all

So in this example your wind is 30 degrees off your course, so apply half the max drift, so you should adjust your heading by 5 degrees (half of 9).
On take off, adjust your heading by 5 degrees into wind to stay on the extended centreline. Of course, on the downwind leg you can just adjust the same amount the opposite direction.
However, don't overthink this - nobody is going to worry too much about a student pilot drifting slightly from the centreline. It's more important to concentrate on your speed and situational awareness in the pattern than being too exact. Your instructor will get you to "tighten" up your accuracy as and when they feel you've nailed the other bits.

@DJClayworth yep of course I did... thanks for catching that.

Problem with this method is that wind at 100ft will be different from that found in metar. 200 even more so and it just keeps getting worse. It'll get you off the ground good enough for sure, but adhering to a numeric value all the way to pattern altitude most likely will not keep one aligned.

@Jpe61 of course you're right, and trying to be too exact about this will just lead to more problems. It's more about feeling what's happening which as I said comes with experience. This method, if using the winds at ground level might give you a good start for the first 100ft or so. ie/ if you know you need to adjust heading 5 degrees left you do so soon after you lift, it might make it a bit easier for you.

You have to establish a crab angle appropriate to the cross wind, same as you establish a crab angle while flying a cross country track with a wind from the side, or a crab angle on final.
So you take off and fly runway heading and immediately find yourself drifting left. Make a coordinated turn to the right, say 5 degrees heading change, then hold that heading. If you're still drifting, increase to 10 degrees, and so on.
Shortly you'll learn to anticipate the ballpark crab angle you need, and make a coordinated turn to the required heading as soon as you are airborne. So light crosswind, turn 5 degrees right, strong crosswind, 10 degrees right. Hold the heading, assess, and adjust as required.
Once you've found how much crab angle to use and have set a heading, look out to find a landmark to use as a reference so you can maintain the heading while keeping your head outside.

The root cause of the drifting is that winds are generally higher as one climbs away from the ground.  This is known as a wind gradient, and it can also affect your glide path on approach to landing.
Expect more control inputs to correct for wind drift as you climb.
As with anything involved with piloting, it is best to be ahead of the issue, rather than correcting after drifting downwind.
Expect your distant reference point to move left or right in the wind shield as you add more control inputs to compensate for the wind drift, and try to fly upwind of it at first.
Practice will make perfect, and it will be helpful to look at a map and pick out intermediate ground points along your flight path to help hold course, such as roads, buildings, parks, etc.
In the future, for longer trips, these reference points may be replaced by radio beacons, but visual navigation will do for now.

The fundamental here is to learn to keep runway centerline during takeoff roll in crosswind conditions. Avoid pumping the rudder but aim to find a constant pressure on the pedal which keeps you on the centerline. Also, if I remember correctly the crosswind procedure for C172 calls for deflecting the ailerons (yoke) towards the wind. The yoke shall be returned gradually to center during takeoff roll so that ailerons are centered at the time of liftoff.
During the rotation, gently release pressure on the pedals and center them. When performed optimally, the yoke and pedals are centered when the main landing gear lifts up and the track of the aircraft is at that moment still along the centerline of the runway.
Once airborne, with correct track and lateral flight controls centered, the aerodynamics will take care of the rest. As the mass of the aircraft is already going to the right direction, the vertical stabilizer will turn the aircraft nose towards the wind to balance the airflow, which is not from straight ahead due to crosswind. Do not prevent this change of few degrees in yaw, as it will automatically put the aircraft on the correct heading to compensate the wind. If any roll is induced, level the wings with ailerons.
Then take a fixed position along the intended flight path and gently make small corrections in the heading with ailerons to keep the desired track as the wind changes as you climb.


text:
STOL AIRCRAFT in Flight
Aviators here is a question. Can you land a "STOL" aircraft in a "C5A Galaxy" while both are flying?

Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking.

Have you looked into how wide the C-5 cargo bay isn't, in the context of "aircraft".

I was rather hoping for a treadmill spinning on the floor of the Galaxy...

Not saying such a thing would be totally impossible, but nope.
Look up the width of the cargo bay of a C5, then look up the wingspan of your favorite STOL plane that you had in mind for this question.
Then look up the approach speed of a C5 and the cruise speed of your subject STOL plane.
There may be other issues making such an attempt highly unfeasible, but those two things would be the main ones to consider, and would rule out any serious consideration.

Not to mention, enjoying the wake turbulence you'd get, flying along closer & closer behind an aircraft that outweighs yours by a couple orders of magnitude... doesn't seem like fun.

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

sort: votes


text:
Help identify low-wing aircraft in 1935 photo

Can anyone help identify this aircraft?  The photo was taken in 1935 in Salinas, California.  I realize it was taken from a great distance, and the resolution is poor.
With my inexpert eye, I immediately thought PT-19, but that didn’t fly until 1940.  On closer inspection, the dual cockpits look like they might be farther back than in the PT-19, but otherwise the form is quite similar.
An unrelated great uncle (relationships are complicated) managed the airport in Salinas and was a flight instructor until WW2. As a child, my mother flew in an open, dual-cockpit trainer with her sorta-uncle at the stick in 1934 or 1935.  There’s a very small chance that this is the same aircraft, but in any case I’d be very interested to learn what it is.
Thanks very much.

"An unrelated great uncle" - Sorry, but what?

@MikeB it's semi common for close family friends to be called Aunt/Uncle, I don't see why this couldn't be extended to great uncle for someone older. Although I don't know why OP bothered to mention they were unrelated.

Part of the low quality of your scan is probably the jpeg algorithm's compression.  It doesn't always handle black and white nicely. If you rescan the original set for greyscale and either an uncompressed format or with the jpeg settings at least set to maximum quality that might help quite a bit.

@Perkins indeed if I had the original photo I’d have created the best scan I could, and I’d have saved without compression. I’m well aware of compression artifacts. Alas this is a crop of an online image at link.

Based on the planform revealed by the shadow, I'd go with an ancestor of the T6 Texan that first flew in 1935, the North American BT-9.
1

Just a comment, but the back of the tail on this is curved, and I can't see a curve on the OP photo. The tail wheel and engine cowl are also a little more distinct, but these are doubts rather than anything stronger.

The picture of BT-14 on the linked Wikipedia page looks identical to OP, down to color scheme

But the BT14 didn't have swept wings, which the OP airplane clearly does.

@JohnK to me these photos look like the wings have some sweep, similar to the original photo: https://commons.m.wikimedia.org/wiki/Category:North_American_BT-14

https://media.defense.gov/2015/Mar/16/2001032109/1200/1200/0/150316-F-IO108-005.JPG  This museum display shows it even better. Looks to me like the main visual difference is the BT-9 has very round wingtips while the BT-14 is more of a rounded-off square. That said if the photo was taken in '35 then it was right around the time of the BT-9's first flight, and that has to be much too early for the extended and up-engined BT-14, right?

The Texan did not exist before December 1940 when the USAAC ordered 400 AT-6Bs. These aircraft were built at NA's Dallas TX facility.  The Dallas facility was initiated because orders for these aircraft exceeded the manufacturing/assembly capacity of NA's Englewood CA facility. The aircraft shown in the photo, above, is documented as US Navy NJ-1 Bu. No 0922 delivered 31Dec1937 & photo'd in flight late Jan 1938.

@MikeB To my eye it looks like the digital compression algorithm of the original photo has blurred the trailing edge of the tail into the landscape.  It might be rounded, or it might not. A fresh scan of the original image into an uncompressed format might help.

@JohnK I see why you suggest it could be a BT-9.  The sweep of the leading edge of the wing and the general planform are definitely close. If indeed the photo is from 1935, that seems to me to be quite early for a BT-9 to be at a civilian airfield in California.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
Who publishes the definition of the shape of a national airspace?
Title says it all.
Who is in charge of providing/defining the official shape of a national airspace?
I guess that most of the times they follow international borders, but there must be a document somewhere stating it, right?
Also, what happens at fractal-like/oddly shaped borders?
See for example the border between Germany and Belgium near Rötgen/Monschau: is the German airspace cut by a sliver of Belgian airspace?
If not, where's the document that says so?

In short: ICAO, a UN agency, is responsible for organizing, with States and Air navigation service provider (ANSP), the global airspace, which is published in the Global Air Navigation Plan.
The global airspace is divided in Regions (FIR) defined according to national borders, as agreed in international treaties, with sensible technical adjustments. A GIS application is available to view all FIR and their boundaries. For the region at Belgium/Germany border:

The formal delineation of the European airspace is found in a Regional Air Navigation Plan: EUR Air Navigation Plan volume 1 (August 2024). Unfortunately the document is missing the actual boundary points for Brussels FIR (EBBU, “To be incorporated”), but Langen (EDGG) points are available. Europe FIR delineation is also available at Eurocontrol (Eurocontrol is the ANSP for several FIR in Europe).

Principles
Airspace delineation follow two principles:

States sovereignty over their national territory

Agreements under ICAO (a UN agency) auspices between regional ANSP.

Sovereignty is stated in article 1 of ICAO Convention on civil aviation (Chicago convention):

The contracting States recognize that every State has complete and exclusive sovereignty over the airspace above its territory.

ANSP agreements are recommended in ICAO Annex 11:

2.11.1 Recommendation.— The delineation of airspace, wherein air traffic services are to be provided, should be related to the nature of the route structure and the need for efficient service rather than to national boundaries.

Note 1.— Agreements to permit the delineation of airspace lying across national boundaries are advisable when such action will facilitate the provision of air traffic services (see 2.1.1). Agreements which permit delineation of airspace boundaries by straight lines will, for example, be most convenient where data processing techniques are used by air traffic
services units.

Flight information regions (FIR)
Global airspace is divided, according to ICAO Annex 11 §2.1.1 Establishment of authority into flight information regions (FIR). FIR over high sea waters (international waters) are said oceanic FIR. FIR are grouped into 9 Global navigation plan regions.
FIR definition by ICAO:

An airspace of defined dimensions within which flight information service and alerting service are provided.

FIR above national territories are usually controlled by a national ANSP (or delegated by a State to another State). Oceanic FIR above international waters, where this is no State jurisdiction, have their control delegated by ICAO to one State, e.g. the north Atlantic ocean is covered by several oceanic FIR delegated to US (New York Eastbound, KZWY), Canada (Gander, CZQX), Ireland (Shanwick, EGGX), Portugal (Santa Maria, LPPO) and Norway (Bodo, ENOB).
Sometimes there is no agreement on a national border, and no FIR can be set for a small area, this is known as a NO-FIR area. E.g. see Why is there a strip of uncontrolled airspace between Russia and Norway?
When possible, especially over high sea areas, FIR and Search and Rescue regions are also made coincident.

Worse than the NO-FIR situation is squabbling over control of airspace, like over Cyprus in the Nicosia FIR where ICAO recognizes FIR boundaries but the Turkish Cypriots don't recognize them and established their own conflicting boundaries. This results in conflicting instructions and lack of coordination between sectors. IFALPA has published guidance for pilots on how to deal with this, but obviously this is not a great situation for safety.

Who is in charge of providing/defining the official shape of a national airspace?

NGA (National Geospatial-Intelligence Agency) maintains an Esri/ArcGIS compatible Shapefile to distribute to DoD vendors.

Also, what happens at fractal-like/oddly shaped borders?

Software vendors make their own decision with customer input on how to handle oddly shaped borders. For example, avionics for one aircraft manufacturer may only support a certain number of polygon vertices on screen at once, so a "smoothing" algorithm is run on the raw data to cut it down to a loadable size. Certain parameters are taken into account to make sure the simplified border is always on one side of the border and never crosses into the adjacent border, so by running this algorithm against two adjacent borders, you can get a "no-man's land" in the middle where you can instruct flight crews to simply avoid flying in.

I've fixed it now, but in general, please remember to use quotes when you're quoting, not codeblocks. codeblocks are not screenreader-friendly in such a scenario

that said, I don't care about software vendors, I'm interested in the official definition.

Sorry for the additional information. The top part still stands true, though the actual data may be restricted if you're not part of the industry. My employer has access so I get the periodic drop as part of my role.

It's officially recognized international agreement-based data, there's no need to be part of any industry to be able to access it, it would kinda defeat the purpose.


text:
What limitations are there in restraining unruly passengers under EASA rules?
Today I saw this tweet:

American Airlines passenger was duct taped to her seat after she tried to open the plane door, then bit a flight attendant.

I showed this to my father (a commercial pilot) and he commented that such restraining measures would not be accepted here and would get (part of) the crew arrested.
I did not discuss this further with him, but can anyone point me to the EASA-land regulation that would hint at this? (if it is valid only in one of the EASA countries I will still accept it)
Said otherwise, what can a crew do under EASA rules to restrain a clearly unruly passenger (say that said passenger tries to operate a door or assaults a crew member) ?

Comments are not for extended discussion; this conversation has been moved to chat.

if downvoters would like to explain what needs to be improved, I'm here.

In general, restraining unruly passengers seems to be allowed in the EU. I could not find anything specific in EASA regulations, except the following item in the list of cabin crew duties:

In  case  of  disruptive  passenger  behaviour:  passenger  management  as  appropriate including use of restraint technique as considered required.

(EASA Easy Access Rules for Medical Requirements - GM1 MED.C.025 (c) (6), emphasis mine)
It seems each country in Europe will have specific laws on arresting passengers. I tried to find the respective UK/CAA law, but I'm not really familiar with UK law and couldn't find it. So here is (as an example), the German law that allows arresting passengers:

§ 12 Duties and powers of the pilot-in-command
(2) The pilot in command may take the necessary measures to avert any individual danger to persons on board the aircraft or to the aircraft itself. In doing so, he has to uphold the principle of proportionality (§ 4). In particular, the pilot may

determine the identity of a person,
Secure objects,
search a person or property,
tie up a person if facts justify the assumption that the person will attack the pilot or third parties or damage property.

(3) The pilot may use coercive measures to enforce the measures. The use of physical force is only permitted if other means of coercion cannot be considered, do not promise any success or are inexpedient.

(Luftsicherheitsgesetz (LuftSiG) - § 12, German Aviation Security Act, translated by Google, emphasis mine)
The type of restraint does not seem to be specified here, as long as it is deemed appropriate. An IATA document indicates that some airlines carry handcuffs for this reason:

9.23  Restraining Devices for Unruly Passengers
Some operators provide restraining handcuffs or ties for cabin crew to utilize in the event that an unruly passenger requires restraining. Cabin crew should be trained in their location and use.

(Cabin Operations Safety - Best Practices Guide)

U.K. law: https://www.caa.co.uk/Passengers/On-board/Disruptive-passengers/ up to 5 years in prison + costs of damage / diversion + fine, I think. Here’s an example of a BA flight restraining a passenger, with no mention of consequences to the flight crew https://www.independent.co.uk/travel/news-and-advice/british-airways-cabin-crew-drunk-violent-passenger-restrain-heathrow-singapore-a8670201.html this article mentions the “Tokyo” and “Montreal” conventions https://www.bbc.com/news/magazine-20940106 but it notes laws of the home country apply.

Surely the core of the question is what is the definition of what is known as "reasonable force". My take is that taping them to the seat was indeed "reasonable" but that the tape around the mouth might not have been. However, we are then talking about a criminal act (use of un-reasonable force) which would only be prosecuted if the authorities deemed it to be "in the public interest" - which is unlikely.

@MikeBrockington while criminal prosecution may not be deemed "in the public interest", nothing prevents the passenger from suing the airline and individual flight crew members personally in civil court.  If it were in the USA, most likely they'd get a hefty settlement. In the UK though, less likely.

@Tim Yes, I saw that CAA page too, but that is not the actual law. It does not specify if and how a restraint is allowed.

@AleksG Passenger would get nothing in the US in any kind of situation similar to this one--except fined and imprisoned or committed. There is a lot of legal precedent for the crew being The Law while on the aircraft, so any legally-permissible action that they tell you to take, you had better comply with (e.g. go to your assigned seat, sit down, and shut up). There is actually a very specific previous question: https://travel.stackexchange.com/questions/12905/under-what-situations-can-a-passenger-be-restrained-by-flight-crew

@MikeBrockington Apparently the passenger was biting and spitting. But even if the passenger was just yelling, in the US all the crew would have to say was that it was a distraction from their normal duties. (And that could be a lot of things--maybe even if it's upsetting other passengers so that the crew needs to help the other passengers.) I would be surprised if there were any aviation laws in any country that DO allow passengers to distract the crew.

@MikeBrockington The image quality isn't very good, but I'm not sure the tape is over their mouth. I think I see their lips, and the tape is on their chin.

@Barmar - I would assume that was just poor application, that it has slipped, but since this is a theoretical discussion, it doesn't really alter my point - "Reasonable Force" comes into play in this sort of situation, whether the applicant is Police (of some sort) or civilian, and it comes with an implied qualifier of 'minimum': if the person is adequately restrained in their chair, then there is no obvious requirement to stop them biting, which makes a gag legally problematic, particularly in the wake of the George Floyd incident.

"I could not find anything specific in EASA regulations..." So, an answer was accepted that doesn't answer the question. Riiight.

@JuanJimenez I cannot tell you why Federico accepted this (ask him), but note that it says "if it is valid only in one of the EASA countries I will still accept it" in the question, so I added the relevant German law as an example.

Partial answer valid for Italy. (See Edit 3 for more general info)
Disclaimer: I'm not a Lawyer, and Italian legislation is a real mess, so any expert in Italian Navigation Laws is welcome to chime in and provide improvements.
I'm going to cite several article of Italian Law, which are in Italian. I won't provide an accurate English translation because juridical translation is very tricky (I have friends that do that for a job and research: you have to match terms AND concepts, and it is not easy at all).
Instead, I will provide short, layman, interpretations of the cited articles, just to give the general gist of the thing.
First of all, before asking what happens to people restraining a passenger (crew or not) you must first establish the jurisdiction under which the plane falls. In Italy this falls under the Navigation Code (Codice della Navigazione).
Art.4 and  Art.5 regulates which laws are applicable:

Art. 4 Navi e aeromobili italiani in località non soggette alla
sovranità di alcuno stato
Le navi italiane in alto mare e gli
aeromobili italiani in luogo o spazio non soggetto alla sovranità di
alcuno Stato sono considerati come territorio italiano.
Art. 5 Legge regolatrice degli atti compiuti a bordo di navi e di aeromobili in navigazione

Gli atti ed i fatti compiuti a bordo di una nave o di un aeromobile nel corso della navigazione in luogo o spazio soggetto alla sovranità
di uno Stato estero sono regolati dalla legge nazionale della nave o
dell'aeromobile in tutti i casi nei quali, secondo le disposizioni
sull'applicazione delle leggi in generale, dovrebbe applicarsi la
legge del luogo dove l'atto è compiuto o il fatto è avvenuto.
La disposizione del comma precedente si applica agli atti ed ai fatti compiuti a bordo di una nave o di un aeromobile di nazionalità
estera nel corso della navigazione in luogo o spazio soggetto alla
sovranità dello Stato italiano, sotto condizione di reciprocità da
parte dello Stato al quale la nave o l'aeromobile appartiene.

More or less these two states that, if the plane flies the Italian flag, then the its Italian territory if it's flying outside any Country's aerial space.
Otherwise, i.e. planes from other countries, fall under the jurisdiction of the country of "plane's flag", but if it's flying over a territory subjected to Italian sovereignty, this is applicable only if there is "legal reciprocity" between that Country and Italy.
Let's assume now, that we are talking about a plane under Italian jurisdiction.
Art.893:

Art. 893 Provvedimenti per la salvezza della spedizione
In corso di viaggio il comandante deve prendere i provvedimenti
necessari per la salvezza dell'aeromobile, dei passeggeri e del
carico.

states that the plane commander must take any necessary measures for the safety of the plane, passengers and load.
Art.1095:

Art. 1095 Inosservanza di ordine da parte di passeggero
Il passeggero, che non esegue un ordine concernente la sicurezza della
nave o dell'aeromobile, è punito con la reclusione fino a tre mesi
ovvero con la multa fino a lire duemila.

The passengers must obey orders (from the commander or the crew) concerning the safety of the plane. Otherwise they may be punished by the law with jail up to 3 months or a fine.
All the above and a bunch of other articles in that Code lead to the conclusion that the commander and their crew have some sort of obligation to carry out "police duty" on the aircraft (at least in some measure), especially when plane and passenger safety is at stake.
This alone would represent a "bonus" in a trial against them if accused of some crime related to the restraint of a passenger that put safety at risk.
For the exact measures the crew can enact, we must turn to the ordinary penal Law concerning self-defense.
Here is a somewhat scholarly article about self-defense law, complete with an historical and juridical analysis.
The core point is art.52 of Penal Code that states:

Non è punibile chi ha commesso il fatto per esservi stato costretto
dalla necessità di difendere un diritto proprio od altrui contro il
pericolo attuale di un’offesa ingiusta, sempre che la difesa sia
proporzionata all’offesa.

This deserves a somewhat literal translation:
[a perpetrator of an act] is not prosecutable if [the perp] was forced by necessity of defending a right of theirs or anothers against a clear and present danger of an unjust offense, as long as the defense is proportionate to the offense.
According to the gist of the analysis in the article, you cannot be criminally prosecuted for any act if all these conditions are met:

You act in defense of a right of yours or of another person's, e.g. the right to live or the right to own a thing.

The danger must be clear and present, i.e. highly probable. It's not enough to just believe or suspect something bad may happen.

The act is necessary, i.e. there are no other feasible ways to avoid the offense, e.g. by fleeing away from the danger.

The offense against which you defend against must be unjust. I.e., you can't cry for self-defense against a policeman trying to legally arrest you or you cannot claim self-defense in a brawl you actively joined.

The defensive act must be proportionate to the offense.

By deduction, then, restraining the problematic passenger in the way the OP showed could be allowed without consequences for the crew, but up to a point.
What I see as problematic is the tape on the mouth, since that could be deemed excessive in court. Once the passenger was duct-taped to the seat it was probably no longer a critical threat for the safety of the plane and/or other passengers. Taping her mouth probably was done to prevent her screaming and avoiding further discomfort to the passengers. But this latter is not probably "proportionate" to the threat and probably not even "necessary".
She could be fined for screaming, but gagging her is quite a drastic action against a whole host of her rights (and even dangerous if she has a condition of some sort), so she could have a point in court about that and the crew could be convicted of "eccesso di legittima difesa" (excessive self-defense) or even worse crimes, since they could have put her health at risk for no reason.
But, as I said at the beginning, IANAL, so anyone is welcome to improve my answer.
EDIT
To address a comment from StephenS:

The passenger was reportedly biting people,  so taping her mouth
arguably qualifies as self-defense.  Also, it could be argued that her
screaming  would interfere with the crew’s duties to make  various
safety announcements to the other passengers.

I'm not saying gagging her was unjustified, I say that it was probably not necessary nor proportionate according to Italian law viewpoint.
Once tied to the seat, biting was no longer a present danger, just keep people away from her. And the screaming interfering with safety procedures is not clear-cut. Maybe she could have been put in a different seat, somewhat isolated from other passengers. They could have shielded the noise using blankets hung near her seat. Whatever.
The point is, once a clear-cut necessity (clear AND present danger) is ruled-out, the only people that can decide if limiting a legal/civil right of a person is justified is a judge.
Notice that the Italian law makes a strong difference between "necessary" and "(reasonably) justifiable". "Necessary" means "You have no other (reasobably) viable alternative", not "that's the most convenient way to handle it justifiably".
Not even police can do that in Italy. Police here cannot even arrest you if you are not found committing a crime "in flagrante". They can only detain you at most for 48hrs for strong suspicion of grave crimes (or for identification purposes, if you cannot show them your ID card or other ID documents, like a passport or a visa), pending a judge to validates the detention (the judge must be notified as fast as possible in those 48hrs. The police cannot delay the notification at its discretion).
Moreover, we have a constitution article that prohibits any mandatory sanitary treatments, unless ordered by a judge and only if there is an explicit law that mandates the treatment. With the pandemic we had quite a debate about making vaccination obligatory, even for a limited group of persons, e.g. doctors and nurse, since the government CANNOT impose that. The parliament had to approve a special law to allow for that.

Articolo 32
La Repubblica tutela la salute come fondamentale diritto
dell'individuo e interesse della collettività, e garantisce cure
gratuite agli indigenti.
Nessuno può essere obbligato a un determinato trattamento sanitario se
non per disposizione di legge. La legge non può in nessun caso violare
i limiti imposti dal rispetto della persona umana.

Translation:

The Republic protects the health as a fundamental right of
the individual and interest of the community, and guarantees
free medical treatments to indigent people.
No one can be obliged to be submitted to a determined
sanitary treatment unless mandated by the law. The law
may not in any case violate the limits imposed by the
respect of human person.

Why is this relevant? Gagging her may be considered a mandatory sanitary treatment. I can definitely imagine her lawyers suing whoever gagged her for violation of constitutional rights or a prosecutor starting a crime investigation about that part.
Please, note that I'm not taking sides of the obnoxious passenger here, just trying to explain that Italy self-defense law is quite restrictive and its application is tricky.
EDIT 2
(To address some comments)
Here is a very relevant article I found on BBC site:
Who, What, Why: Is it legal to restrain air passengers?
It supports my points about the rules being fairly country-specific.
Some excerpts (emphasis mine):

So is the level of restraint shown in the photo - including gagging -
allowed by law?
A number of conventions - including the Tokyo Convention (1963) and
the Montreal Convention (1971) - address the issue of ensuring safety
and discipline on board a plane.
[...]
He says that while aviation is international by nature, there is no single over-riding convention regarding the treatment of unruly passengers.
Passengers' behaviour is subject to the laws of the country in which the plane is registered, says Healy-Pratt. And what the crew can and cannot do is also governed by the national laws of that country.
[...]
"Reasonable force can be used but if the crew go beyond that and unreasonably cause injury, they could be held responsible under the Montreal Convention," says Healy-Pratt.
This offers compensation "in the event of damage caused to passengers during international air transport".
Excessive restraint or gagging has the possibility to cause injury and even death.

What's described in this last sentence is what could, by Italian law, tip the scale toward "not proportionate", hence not "rightful self-defense".
Edit 3 (further research results)
Upon further research, I found that all EU states have committed to a new protocol that address the issue of unruly passengers. This a link from the EU parliament that states this.

Subject:  2014 Montreal Protocol, unruly passengers on board aircrafts, Commission's awareness campaign on safety
Answer in writing
Unruly behaviour on board aircraft has significantly increased over the past few years. The International Civil Aviation Organisation (ICAO) has identified ‘unruly’ passengers as a major issue for aviation since they endanger the safety of both passengers and crews. In 2014, ICAO states — including the 28 EU Member States — adopted the Montreal Protocol, which amends the 1963 Tokyo Convention on offenses and certain other acts committed on aircraft, and puts in place a stronger international legal framework to deal with unruly passengers. Given the importance of this new protocol to improving the safety on board aircraft, could the Commission provide an update on the status of its ratification within Member States? What is the Commission’s position on the protocol?

The problem with EU legislation, is that to be effective it must be ratified by each individual country.
Anyway, further investigation into ICAO website brought up this page (Current lists of parties to multilateral air law treaties ). If you scroll down, it reports that the Montreal protocol of 2014 is currently in force since 2020-01-01. There you find a link to a document listing all the countries that signed that protocol.
And this is a relevant document (a PDF slide collection) from IATA.
Regarding the first part of this answer, that document from ICAO doesn't mention Italy. So it seems that my considerations still stand.

The passenger was reportedly biting people, so taping her mouth arguably qualifies as self-defense. Also, it could be argued that her screaming would interfere with the crew’s duties to make various safety announcements to the other passengers.

If I've watched enough documentaries where people had to be restrained, the tape to the mouth would be to stop spitting and/or biting. In a global pandemic, I suspect even this would be justified with the lack of a spit hood on board.

@StephenS, please see my edit.

@Jamiec, please see my edit. And no, tape over the mouth cannot be justified by the pandemic in Italy. If you do it for medical reason, it is a mandatory medical treatment (covered by constitution) and you must consent to it (as when you are in a hospital and they put you in isolation) or a Judge must decree it. NO EXCEPTION. It is not a clear and present danger, unless you can prove the passenger IS infected (and you know it before gagging him).

@Jamiec I know this can be surprising to people from countries where police have much more leeway in restraining people and/or using force (USA come to mind), but this is not how it works here (at least ideally, then we have our share of police abuse).

I don't think your edit adds anything to this answer. there is a lot of conjecture in that edit.

@Jamiec No, there is no conjecture (barring I'm not a lawyer, so there could be lots of details I'm missing), I linked to sources that explain that (sorry for them not being in English). Moreover I also edited-in a part of our constitution with translation. That article is extremely explicit. I admit not every Italian law is strictly constitution-abiding, but the legal basis for what I said is there.

I said in the edit - the main answer was indeed well referenced. Basically everything after I'm not saying gagging her was unjustified,

@Jamiec Yes, I've got that. But I contend also my edit was relevant. If you reread the question, the OP cited his father saying "here" (in his country, I guess) the crew could get arrested. Then the OP was looking for regulations at EU level (EASA) that could clear the situation. My point was that there is no complete EU-level regulation for that, since above a certain level of restraint country-specific criminal law may kick in. Specifically, the edit was focused on explaining why the gagging was particularly troublesome for Italian law. My 2nd edit was made to reinforce that point, too.

As always in EU, "the defensive act must be proportionate to the offense". This is a key point, and indeed difficult to assess. When people are found guilty in a self defense case, this is often because this proportionality wasn't applied, e.g. someone hurts someone else because they were insulted.

@mins Yep. It's a very delicate subject. I can't say if the "proportionality principle" is something that stemmed out of EU regulations, but I remember problematic self-defense cases making the news since I was a kid (EU didn't exist then; it was just EEC). So I suspect that principle was in Italian laws still then. The subject is so sensible that there are a couple of Italian populist right-wing parties that made quite a fuss about "honest people unable to righteously defend themself from robbers and assailants without being prosecuted". ...

@mins ... Then (years 2000?) the law was changed a bit, making it a little more "defender-friendly", especially when the defender is attacked in their home or private property. Still, it's nowhere near USA situation, where in some states (as I get it) you can shoot anyone who entered your property uninvited.

As with the FAA, EASA places the responsibility for dealing with this issue on the crew, and does not set limits on what the crew of an aircraft can do to ensure the safety of the flight. Given the fact that EASA has an official "zero tolerance" policy towards unruly passengers, I would assume that if a passenger tries to take it too far, the crew (and other passengers) will respond in kind, up to and including the use of deadly force if necessary.

@DigitalDracula I'm no expert in European law, but I'm pretty sure that you're allowed deadly force in self-defense. And since a sufficiently determined passenger could, in theory, cause enough damage to crash the plane and kill everyone on board...

"Self-defense" is when there is an imminent threat for life and no other apparent mean for preventing it. Very few cases justify this in EU (not in Europe, there are other European countries which are more tolerant). This also applies to police. That's a good thing as we know some persons are anxious to have their 15 minutes of fame to make their life more interesting.

I asked for specific regulations. "I would assume" is not really that. do you have any other source, like the ones Bianfable provided?

@DigitalDracula EASA does not prohibit flight crews from carrying firearms in the cockpit. That is up to the individual airlines. But why do you think they have them if they do? To use them as props? "Fairly certain" doesn't cut it.

@federico If you don't like the answer, don't accept it. You know that's how it works here. Airline rules on responsibility for the safety of the aircraft, crew and pax are pretty much universal around the world. They also apply to other forms of transport. If you don't think they are, it is up to you to find the exceptions. Besides, you will find few instances in which people not on the aircraft will second-guess the actions of flight crew in a situation of an unruly/dangerous passenger.

I'd assume that "deadly force" is not necessarily talking about firearms here.  Firing a gun in a pressurized aircraft is just a bad idea in general.  I think you'd want to stick to blunt-force and/or wrestling pins to avoid endangering the whole plane.  And while even those could prove lethal, you'd hope it wouldn't have to come to that.

Regarding use of deadly force, as aviation law pretty much anywhere states, PIC may take "the necessary actions to ensure safety of...", it does not rule out the use of deadly force. Lets say the plane was boarded by a person with a firearm. Should this person start acting irrationaly, and maybe even shoot a fellow passenger, I bet my bottom dollar "necessary actions" in this case include anything, even killing the attacker.

@DarrelHoffman The part about firing a gun in a pressurized aircraft being dangerous is at least 99% Hollywood myth. A bullet-sized hole is nowhere near sufficient to depressurize an airliner, let alone crash one. The outflow valve already has a hole bigger than a bullet hole. Plus, a bullet hole would be extremely easy to plug. The pressure difference means that anything you place against it will be firmly held there. The main safety problem with firing a gun in an airliner is not that it's pressurized, but rather that it's packed full of people who you presumably don't want to hit.

@reirab Well, that or you could hit a window, which would result in a considerably larger hole.  Or the bullet could nick some critical electrical wire or a fuel/hydraulic line or something.  I know the whole "getting sucked through a tiny hole" thing like the end of Goldfinger isn't accurate, but it's still not a good idea.

Tests have been performed to see what happens when you fire a bullet at an aircraft cabin window. The answer is "not much" because the windows are laminated inside and out. If there is depressurization, it will likely not be explosive. Masks will be deployed and the pilots would initiate an emergency descent. As to aircraft systems, the critical ones have dual or triple redundancy on modern airliners. Anybody crazy enough to do that would likely be aiming at people, more so when the crew and probably more than one pax will be trying to disable them.


text:
Constructing flight recorder data
By just going off the public information about a flight and what one knows about an aircraft, is it possible to construct a differ version of a flight recorder's data well enough to fool investigators?

Note that while CVR and FDR are vital for analysing of accidents involving pilot error or system failure, they don't have much relevant data for explosions and mechanical failures. For those traces on the debris characteristic of various causes of damage are most important. And in case of shot down debris of the missile and any radar recordings, videos or photos that may have captured the missile. So in case of MH-17 the investigators are likely to primarily look for different kinds of evidence.

Theoretically? Yes.
Practically? No.
In order to construct an alternative Flight Data Recorder narrative good enough to fool investigators you would have to acquire a flight data recorder to feed the data to (this is the easy part). You would then need to feed the appropriate parameters to the flight data recorder to fill its memory (modern recorders can hold over 10 hours of data - this could encompass several flights that would have to be believably reconstructed - speeds and altitudes matching radar track data for example).
A flight simulator could probably be rigged up to supply the data to the recorder, so the primary difficulty here would be matching your forgery to other data sources like RADAR tracks, radio calls, the CVR (unless you intend to falsify that as well), etc...
Once filled with your falsified/reconstructed data the recorder would need to be injected into the chain of custody, which is perhaps more difficult. replacing one which has been recovered would require fooling the investigating agency, which has already seen, photographed, and cataloged the device they recovered (and would likely notice any subtle differences), or by finding the real recorder before investigators and replacing it with your forgery.
While it is not impossible to do all of the above it is highly unlikely that anyone would succeed in such a scheme.

Wouldn't "finding the real recorder before investigators and replacing it with your forgery" also involve forging or at the very least gaining access to aircraft records to match up things like model, serial number, etc.? Surely those are checked by the investigators soon after recovery of the recorders? Also, I expect those are kept in several places; with the aircraft manufacturer and with the operator (if nothing else then from the most recent D check or similar), at a minimum.

@aCVn: It's not that hard for the serial number on a flight recorder to be obliterated by impact and/or fire, and a mismatch between the flight recorder model in the aircraft records and the model of recorder recovered would probably just be chalked up to a recordkeeping error.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
Why don't they have two black boxes?
Why is it that black boxes don't float?
From what I gather the answer is:

So they will not float away from a water crash site. The ping can be heard underwater with sonar. Finding the ping, finds the site.

But why not have two black boxes one that floats and one that stays with the aircraft?
That way if a plane is lost at sea, if we find the black box floating, we could use the data to find the other black box and the crash site. Plus the benefits of having a redundancy are enormous.

for the record you are counting the FDR and CVR as one set of boxes right?

@ratchetfreak yes both of them, but I believe it's a CVR

It is true that most CVRs and FDRs are technologically backward.  The industry is starting to question why they are fitted at all.  The technology exists to transmit the key data points (you don't need it all) to external storage, by data link when available, by satellite when not.  I expect (OK, guess) that the next generation of aircraft will bring data logging into the 21st century.  It's already done to an extent for the engines.  It's only time before the rest catches up.

The added weight, space, and complexity of a second recorder have to be taken into account, and all are very important for an airplane.
If you are just interested in location, then there could just be a simple beacon designed to float. Although less, this will still have the above costs. And you have to design something light enough to float, sturdy enough to survive an extremely violent crash, yet still be a functional electronic device.
Considering that the situation of a lost aircraft at sea is fairly rare, it is questionable whether the benefits justify the costs.

Although circumstances of a lost aircraft at sea are fairly rare, the cost of searching for one is enormous... The cost to find air france was about $50 million, and I am sure flight 370 will be much greater... It might be fairly rare, but it's expensive.

True, the search is very expensive. But designing a beacon, certifying it, installing it on the fleet, and flying it around and maintaining it will add up very quickly. And unless it is somehow mandated, it will be just like the services we have available today that airlines don't want to pay for.

How much would it cost to have both black boxes record both flight data and the cockpit audio, rather than having one for each? Having separate boxes for data and audio may be better than having one for both, in that it maximizes the likelihood of recovering at least something, but having the boxes be fully-redundant would seem like a cheap way of maximizing the likelihood of recovering the most interesting information.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


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Missing position (lat/lon) in ADSB data
I would like to ask if anyone has encountered latitude longitude (Data Item 021/130) missing in ADSB data, specifically in asterix cat 21. In addition to the mandador entries, there is also geometric and barometric altitude or flight identifiers available in the data, but the lat/long position is missing. Is it possible for the pilot to disable the sending of the lat/lon position in the ADS-B data?

What brand/model of receiver do you use and which ASTERIX Cat 21 edition does it provide?

ADS-B transmitters can transmit NO-Position messages (FTC=0) if the source of position data does not provide position data. This can happen when GPS is unavailable (e.g. due to jamming). In some installations it may be possible that the pilot switches the position data off. This is however non-standard.

Wow, can it really happen that the pilot switches off only the position sent in ADSB? What does the aircraft have to be equipped with for the pilot to be able to do that? Thank you for your answer.

On some state aircraft it is possible to switch ADS-B position. It requires an additional switch/controller in the cockpit. Very rare to see this. I think it is more likely that you have seen a case where GPS position was not available to the transponder. If you are not too far from a war zone (e.g. Ukraine), it could well be an effect of GPS jamming. Or there can be faulty logic in the ADS-B receiver, and there are a few other cases that may trigger this in a well functioning receiver. What make/model of receiver do you work with. Which Asterix 21 edition?


text:
North Atlantic Tracks entry and exit points
Are the actual locations of the North Atlantic Tracks entry and exit points published anywhere? I'm looking for definition (latitude, longitude) of the entry and exit points for North Atlantic Tracks.

Where to download NATs (North Atlantic Tracks) information?

You can find the routes them selves here, the start and end points are noted like other airway intersections by phonetic names. You can look up the names here (use world hi maps to see them) for exact locations. For example you can see a route start at TUDEP and if you take a look on SkyVector you will find (lat/long in the top corner):


text:
Relation between Saab B3LA concept aircraft and AMX International
The Saab B3LA aircraft concept and the AMX aircraft were developed around the same time and out of similar requirements.
According to the Swedish Wikipedia:

The [B3LA] project was abandoned in 1979 in favor of the Saab 39 Gripen, without any prototype being completed. The project was partly a collaboration with Aermacchi. When Sweden pulled out of the project, Aermacchi found a new partner in Brazilian Embraer and their AMX aircraft is largely built on the basic design from the B3LA.

(My translation)
This is given without any reference. I can also find this "fact" in other places on the internet, without references.
Was the AMX actually a continuation of the B3LA or are the designs similar because of similar requirements and the available techology at that time?

I can't find anything even on Italian sources related to the participation of Aermacchi to the B3LA project.

Also, AMX started in 1978, one year before the cancellation of the B3LA which would be strange if it's the same project. I suspect that the wikipedia sentence may be incorrect or speculation.


text:
Holding time during static structural testing of a composite wing
While doing a static structural testing of a composite wing (high aspect ratio or otherwise), is there an industry practice or standard that determines the holding time for which a load is applied through whiffle tree. Specially, when we reach the DLL or DUL. Would keeping the wing deflected at DLL or DUL for longer duration that is few minutes make any difference?

The testing of composite wings I witnessed held the highest load for three seconds in order to pass the test. If you put high loads on a composite structure for the first time, you will get some minor cracking as the local peak loads get "re-routed". This process takes only a very short time, so three seconds were considered enough for this re-routing to finish.

Probably not. It's pretty much implied by the word "static" that this is an all or nothing proposition.  Either the structure will fail more or less immediately upon reaching the maximum load, or its good for a long period of time.  1 minute versus 1 hour will not make any difference.  Now, if you were to hold the load for a VERY long time (say a few years) then the polymers in the matrix would eventually creep.  But that's not really a relevant load case for a wing structure.


text:
How do after-burners work on jet planes?
I've always wondered this after getting introduced to fighter jets, the sheer concept of being able to create a larger "exhaust" out of a fighter jet and cause it to speed up has always just not made sense in my brain. I was wondering if anyone could provide an easier-to-understand answer since most of the answers I've gotten from friends and family don't make that much sense to me. Thanks to anyone who can help me with this.

In the explanation at Wikipedia, what is unclear? https://en.wikipedia.org/wiki/Afterburner

Maybe this answer helps.

The hot, fast-moving exhaust from a turbojet contains lots of excess oxygen with which more fuel could be burned, if you wanted to. And with no turbine wheel(s) immersed in that superhot exhaust (downstream of the last turbine stage) you can go ahead and spray in more fuel, heat the exhaust up even more, causing it to expand and accelerate even faster out the exhaust nozzle, thereby generating extra thrust.
In terms of thermodynamic power-extraction cycles, afterburning is called reheat.


text:
What is a "rapid changes in gravitational force"
I've been reading an article on the BBC Website about the 21/May/2024 incident on Singapore Airlines. According to this article:

"The rapid changes in G over the 4.6 seconds duration resulted in an altitude drop of 178ft (54m), from 37,362ft to 37,184ft," the TSIB report said.

and

The Transport Safety Investigation Bureau's (TSIB) preliminary findings found rapid changes in gravitational force (G) and the altitude drop ... likely injured those who were not wearing seatbelts.

My knowledge of physics tells me that the gravitational force is dependent on the masses of the two bodies (the aircraft and the Earth), the distance between them and 'G' a universal constant. Given the the Gravitational constant can not change and mass of the Earth is so much bigger than the other variables then in practical terms gravitational force should not be changing.
So what are they really saying is the problem?

G is not gravity in this instance but g-force:  a force between a human body and another solid object: eg. your seat or seatbelt. For example if you drive your car and suddenly brake you will feel a strong force pulling you forward against your seatbelt. That's what G refers to.

This sounds like a poor translation

The TSIB preliminary findings and the BBC use "G" as a short-hand for g-force, which is not the same thing as "gravitational force". They are using the wrong terminology here.
The g-force is actually a measure of acceleration and not a true force at all. This acceleration doesn't necessarily come from gravity alone, it can include other accelerations.

The g-force or gravitational force equivalent is mass-specific force (force per unit mass), expressed in units of standard gravity (symbol $g$ or $g_0$, not to be confused with "g", the symbol for grams). It is used for sustained accelerations, that cause a perception of weight. For example, an object at rest on Earth's surface is subject to 1 g, equaling the conventional value of gravitational acceleration on Earth, about 9.8 m/s².

(Wikipedia: g-force)
The actual gravitational force did not change at all during this incident. The acceleration the aircraft experienced was due to "an area of developing convective activity" causing severe turbulence, i.e. a result of the interaction with the surrounding air, not gravity.

In short
BBC describes the force variation on persons and objects during the turbulent/windshear event. They say the magnitude was subject to rapid changes.
This force is sometimes called the g-force, it results from an acceleration of x g units (e.g. 2g). The confusion between unit of acceleration g and gravitational constant G is usual in aviation, and in other domains. But sometimes the correct unit is used, like in this profile of a parabolic flight:

(Source.) Note the force is always positive, it's a magnitude, not a vector.
The g-force corresponding to the regular weight is 1g. It's a unitary quantity (the force exerted on a unit of mass), and unless the direction is specified, e.g. $g_z$, it should be understood as a magnitude.
The force created by all accelerations on a body cannot be split between gravity and other causes. The resultant is perceived as a weight. If one says the force is 3g, it means something like "the magnitude of the force on any object of any mass is 3 times what it would be if the gravity were 3 times stronger". Perhaps this force is upwards.
This is rather informal and only aimed to provide an idea of the scale: A person would feel as if their weight was multiplied by 3, whatever their weight is. A person aboard the ISS is subject to 0g, and feels weightless (in the rotating reference frame neither the gravity nor the weight have actually changed, but another force, the centrifugal force, is cancelling the effects of gravity).
Details follow.

Some definitions
G constant: A constant which value is 6.674e-11 N.m²/kg². As we can see time is not part of the dimension, hence it's neither an acceleration (dimension m/s²) nor a force (N). This constant is used to calculate the attraction force between two bodies.
g: A unit of acceleration, a multiple of the regular SI unit (m/s²): 9.81 m/s². An italic is used to differentiate this unit from the SI unit gram.
Why this unit? When one of the two bodies is much larger than the other, like Earth compared to objects on Earth, it's convenient to see the attraction of gravity as resulting only from Earth. Seen like this, the force "exerted by Earth" has a value equal to 9.81 times the mass of the small object, and is called weight. Earth mass and distance have been removed from the equation. We say Earth is pulling the object at a rate of 1g. Technically the unit $g_0$ should be used to talk about Earth gravity acceleration, g should be used only when other accelerations are added.
Note in aviation field, g is often misspelled G.
g-force: It's the force pulling the object, created by the sum of all accelerations. Some of these accelerations are due to gravity, but other are due to body displacement. Related to the load factor: A load factor of 2 means a g-force of 2g.
Let's say we are in a lift going up with a velocity increasing by 9.81 m/s each second. Our body senses the weight due to gravity, and also a force from the lift floor which magnitude is equal to the weight. This force is due to the acceleration of the lift, not to gravity. Still we feel like our weight has doubled. We say the g-force is 2g.
Applied to turbulence
In this case air had an unusual vertical velocity in the vicinity of a jet-stream, creating a strong erratic wind (windshear). This can happen from 6,000ft below the tropopause to 3,000ft above. This is called clear-air turbulence (CAT), in contrast with the usual turbulence occurring in visible clouds.
The aircraft still fly within this moving air at its constant cruise airspeed, but w.r.t. the ground, the aircraft velocity is the vector sum of both velocities. This velocity is erratic, meaning the aircraft is accelerated, like our previous lift. The direction of this acceleration is also erratic, so the g-force exerted by the aircraft on passengers and objects is erratic, pulling/pushing passengers and objects in erratic directions.
So the mechanism is not the "The rapid changes in G over the 4.6 seconds duration resulted in an altitude drop".

G has nothing to do here, it should be the g-force or the total acceleration (which includes gravity, but also accelerations not related to gravity).

The g-force doesn't create the change in altitude. It's the contrary, the change in altitude creates the g-force.

The change in altitude is due to the vertical windshear associated with the turbulence.

Acceleration magnitude
The BBC article mentions 54m in 4.6 seconds. Assuming the velocity changed at a constant rate, this is an acceleration of -5.1 m/s² or -0.52g. The resulting g-force was equivalent to 0.48g.
People were injured by floating objects, because the acceleration changed a lot during the 4.6s, possibly in a range of several g. The danger is from persons and/or objects meeting with different velocities.
CAT
The intensity of CATs is predicted to increase as atmosphere temperature increases, and could be a real problem for aviation in the future.

If g-force is a force then it cannot be expressed in units of g. F = ma, and only a can be expressed in units of g because both a and g are in m/s^2 or ft/s^2, so that g-unit = a/g = ma/mg = F/W.

@LJQCN101: As indicated g is an acceleration but g-force is a force. When a doctor says the blood pressure is 70 mm of Hg, they are expressing a pressure (which unit is Pa), not a length. This is the same here. Some equivalence is used. It's not very scientific and it's confusing.

"The force created by all accelerations on a body cannot be split between gravity and other causes." Acceleration does not create force. It's the contrary, force creates acceleration. And forces on a body from its center of gravity can definitely be split between weight and other forces. By simply dividing the forces by mass, you get gravity and other accelerations caused by those forces.

g-force or load factor $n$ = (total acceleration minus the acceleration components due to gravity) / g. It is an acceleration expressed in g-units, or multiples of 9.81 m/s^2.
In the equation $n_z$ = Lift / Weight, lift does not include weight ( = mass * gravity acceleration) component, so when people are using this equation of load factor, they automatically exclude the gravity component.
Why the exclusion from total acceleration? Acceleration due to gravity and inertial forces do not create or create very little internal stress at any internal point of an object, as the forces pulling each internal point are equal. While load factor is about motions that create internal stress in an object, so that such accelerations must be excluded when calculating load factor due to motions.
The equation $n_z$ = lift / weight can also be interpreted as, aircraft or person feels X times the weight of itself opposite to the direction of lift. Consider an aircraft in a 2g coordinated turn with constant speed and altitude, then $n$ = $n_z$ = 2g as lift is pointed vertically in the aircraft body Z axis, while $n_y$ = 0g because no side acceleration in a coordinated turn. The person feels the acceleration downwards to the floor of the aircraft, opposite to the lift direction. In this case it is not to the direction of gravity nor centrifugal force.
With an object resting on the ground, the total acceleration is 0 m/s^2, and the acceleration excluding gravity component is 9.81 m/s^2 upwards due to the opposing force of weight when an object is contacting the ground according to Newton’s third law, so $n$ = 9.81 upwards / 9.81 constant = 1g.
With an object in a low orbit at ISS, the total acceleration is mostly centripetal acceleration, which is the gravity, as the object is not moving in a straight line, but in an orbit. And the acceleration due to gravity is excluded from the equation, so that $n$ = (g - g) / g = 0g. Inertial forces like centrifugal force is not relevant here.
It's also very important to clarify which direction the acceleration it is referring to. In the case of acceleration directly sensed by the accelerometer, they're body axis acceleration, or $n$ w.r.t the aircraft body: $n_x$, $n_y$ and $n_z$.
The vertical acceleration, or normal load factor ($n_z$) is widely displayed in the cockpit instruments or used as a feedback by longitudinal control systems. This answer provided some examples of the usage of $n_z$ in certain fighter aircraft.
There's also side acceleration ($n_y$) that is not displayed to the pilot, but can be used by directional control systems to provide turn coordination.
A decomposition of $n_y$ and $n_z$ is provided by NASA TM-107601

In which:

g is the constant acceleration due to gravity of 9.81 m/s^2.
q, p, r are body axis pitch rate, roll rate, yaw rate respectively.
u, v, w are body axis velocity in the body X, Y, Z axis respectively.
the dot above u, v, w means derivative of velocity, or acceleration in the body X, Y, Z axis.
lyz, lzz are vector transformation from the local (Earth) axes to the body axes.
glyz, glzz are the components of g in the body Y and Z axis respectively.

So if not considering angular rates, $n_z$ can be expressed as (w_dot - glzz) / g, or (body Z axis acceleration - body Z axis gravity acceleration component) / gravity acceleration.
It is a/g in short, so $n$ can also be calculated using Force(=ma)/Weight(=mg), which is, total forces excluding weight, divided by the weight of an aircraft.
That’s why $n_z$ can be expressed as Lift / Weight.

"g-force = acceleration excluding gravity component" Do you mean the g-force in the ISS is not 0g (micro-gravity) but -1g, the value of the centrifugal acceleration?

@mins It’s still 0g if excluding gravity component. Check the NASA equations. An aircraft flying straight and inverted experiences $n_z$ of -1g.

"It’s still 0g if excluding gravity component" To get 0 g I need to sum centrifugal and gravity accelerations which are opposite. For the inverted flight in straight line, adding centrifugal acceleration 0 g and gravity -1 g (in the aircraft frame), also works. Both examples contradict your premise of excluding gravity acceleration from the sum.

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Relativity states that the so-called force of gravity is not a force, but an acceleration due to the distortion of space time.
There is no physical difference in between gravity and acceleration, or free-fall and zero G.This is known as the equivalence principle.
So if you believe the physics, yes, gravity as experienced by the people inside the plane changed, but the article incorrectly describes this as a force rather than acceleration.


text:
Would a removable door frame improve the safety of a fuselage door plug design?
The 737 fuselage door plug has the dubious distinction of failing in the same direction it was designed to be installed or removed ... from the outside.
An analogous design is mounting a truck tire and rim onto an axle with many bolts, that are carefully torqued to spec.  Steering systems take it further with castle nuts, with a cotter pin through the bolt to prevent the nut from turning.
In housing construction, carpenters build frames to hang doors from.
Which leads me to wonder:
1. Could they not build a beveled frame for the plug so the door could only be pulled to the inside even if all bolts failed?
2.  Would more bolts (like 14) make the existing design safer?
The "bevel" frame could be changed out with a regular door frame as needed.
Pressure differential between cabin and outside would make the beveled door almost impossible to open at altitude.
Some numbers:
The plug 6 foot × 2.5 foot × 12 inch × 12 inch = 2160 inches$^2$
Pressure. 8000 feet:   11 psi
Pressure 40000 feet :  3 psi
2160 inches$^2$ × (11-3 psi) = 17280 lbs
That door ain't moving.

What would prevent the beveled frame from separating from the fuselage?

@A.I.Breveleri  One possible design (as the bevel would be to the inside) might be to put a flange or a lip on the inner edge and have like 30 bolts all the way around to the door frame.

A lot of main doors and most service doors are the same type of "plug" door. They aren't true plugs as in a cork stopper, that has to back away to be opened. Some main doors and most emergency exits are made that way (like a cork), but they have to move inward and rotate to be opened (or rotated and tossed out in the case of an emergency exit), but main doors designed to open outward after moving in and turning are less common now. Service doors are typically lift-and-out plug doors and will use a large swing arm to let the door move out and completely outside of the way so that servicing platforms can back right up to the door sill.
These doors are still considered plug doors because cabin pressure still pushes them against the fuselage structure, but it's in the form of stop fittings that can be cleared by lifting the door, so the door structure doesn't have to be wider than the opening and it can open straight out once lifted.
When I look at the pictures of the "door plug" on the 737, it looks like just a version of the normal operable door that swings straight out and down after being lifted, but which is installed with blocker bolts in the upper roller tracks to prevent the lifting mechanism from being operated. Even with the blocker bolts missing, it's a mystery how the door could open on its own with one or two thousand pounds pushing on it as soon as the airplane pre-pressurizes during takeoff, increasing to about 5 tons at 14000 ft. When it's not lifted clear, it works the same as a cork style plug door, with cabin pressure pushing the door against the fuselage structure, except the loads are going through overlapping lug fittings spaced along the frame, instead of the entire door perimeter.
Anyway, there seems to be more to this story than meets the eye.

OK the "bolts" seem to act more as "cotter pins" rather than directly being pressure loads.  But only 4 of them?  One might consider bolting the stop pads too (once they are overlapped after the door drops in).

There will be lugs all down the side of the door frame. The bolts in question are blocking the exit of rollers from L shaped guide tracks at the top.  There is some evidence the bolts holding the tracks themselves were loose. I can see that if that happened and the door was able to jiggle up and down when unpressurized, the load bearing cleats might be just overlapping slightly when pressure is applied, and it hung on for a while until boom. All to say there's nothing wrong with the basic concept, as it's used with success on most pressurized doors.

that makes sense. Upon further review of the design it looks like there are 2 hinged pins at the bottom and a drop in guide on top with the 4 bolts preventing upward movement of the door.  This would make the top guides critical.  Absolutely.  Even though the bottom bolts hold the door to the pins ... this one hurts.

The main airstair door on the CJRs isn't a plug at all. It's just a door with big pins that stick out into the frame at 6 places, a piano hinge at the bottom and a kind of retainer cam at the top. When pressurized, the shear load on the pins makes it impossible to move the mechanism to try to open it. When open, the door actually rests on the ground with a little roller foot thing that flips out.

Would it improve the safety, maybe.
Many aircraft doors are indeed "plug type" doors for this reason and must first be opened into the airframe, rotated a bit then can be pushed out of the airframe. However the critical part of this design is that it provides a neat failure option on something that ultimately needs to open and close.
Door plugs on the other hand are panels that are intended to fill an area where a door would have been and thus generally don't open and close and can rely on other methods of mounting that may make servicing easier. In aviation weight is a considerably important factor when designing parts, as such cap pieces like the door plug in question will be designed to operate correctly and be as light as possible. There are plenty of places where redundancy can be added to aircraft in the name of safety but one must understand the implications of over complicating a design.
There are pressurized airframes out there that utilize non plug type doors with other locking mechanisms and have flow quite successfully for an enormous number of flight hours indicating that there are ways to safely design a door plug that can be installed from the outside.

From your reference:  door plugs are designed to permanently seal off optional exits door openings.  Why not do it right? (But I do agree with your last sentence).

@RobertDiGiovanni No, not permanently. The point of the plug is so that the plugged opening can later be converted to a door, if the seating configuration is changed so that the extra 2 exits are needed. The plug is fairly permanent in that it isn't expected to move or be opened for a long time, but the option to swap it over to a door is there. Which is why it isn't, for instance, welded into place with everything in contact where it needs to be.

@RalphJ that's the mystery to me.  A beveled design would be even easier to remove if the aircraft was re-configured.


text:
What is the squawk for VFR flying?
I'm used to using squawk 7000 for VFR flight. But lately I've seen 1200 also being used. I don't know which one is the default for VFR flying, because it seems like both codes are widely used.

What country are you flying in?

Ah, I knew you would ask that. The thing is I fly in multiple countries, and I need to determine what are the different codes in general. I mainly fly in the US and Canada, and I've seen both 7000 and 1200 there.

Are you on flight following or not?  ;)

@MichaelHall Nope. I guess I could use flight following and then they would tell me a squawk :)

It depends.
Generally, when receiving air traffic service (such as air traffic control) a specific SSR-code will be assigned, allowing ATS to identify the flight using surveillance equipment such as RADAR.
If flying in an area without ATS or when no specific code has been assigned, each country will have one or more specific codes the pilot should transmit by default. These codes can be different in different parts of the world, and you would need to check the AIP for the country in question in order to find the correct code. This is an example from AIP Denmark (ENR 1.6):

f. Pilots, who have not received specific instructions from ATS concerning the setting of the transponder, shall operate the transponder as stated in the following:

IFR flights within København FIR:
Mode-A, Code 2000.

VFR flights within København FIR:
Mode-A, Code 7000.

MIL VFR flights within København FIR:
Mode-A, Code 0001.

Helicopter engaged in off-shore operations:
Mode-A, Code 0040.

In many parts of the world - like in Denmark - the default code for VFR flights is 7000. One notable difference is the USA, where 1200 is used. However, again, you need to check the rules for the actual country in which you are flying, as regional rules can be different.

1200 in US, CA, AU. 7000 in ICAO, EASA.

@300D7309EF17 ICAO isn't a region. ICAO procedures apply worldwide, including in US, CA and AU. Individual countries decide which parts of ICAO SARPS to implement.

@300D7309EF17 So basically north america and australia uses 1200, and the rest of the world 7000?


text:
What is the definition of in-flight for the purposes of a fire?
Reading 49 CFR 830.5 I am trying to determine the definition of "in flight" and "in-flight" used in the Immediation Notification sections 49 CFR 830.5(a)(4) "In-flight fire" and 49 CFR 830.5(a)(5) "Aircraft collision in flight".
In 49 CFR 830.2 “Aircraft accident” is defined as "...an occurrence associated with the operation of an aircraft which takes place between the time any person boards the aircraft with the intention of flight and all such persons have disembarked..." which is a possible answer but this section is very specific to accidents and does not mention "in flight" at all. The other possible definition might be 14 CFR 1.1 “Flight time” "... Pilot time that commences when an aircraft moves under its own power for the purpose of flight and ends when the aircraft comes to rest after landing ..." but this seems very specific to the logging of time.
In flight does seem to have a pretty common sense definition but I due to some grey areas around taxi/start-up I can think of I am surprised I cannot find an explicit definition.

Other uses of "in flight" make it clear that operating on the surface does not count as "in flight." For instance, from 91.113(g):

Aircraft, while on final approach to land or while landing, have the right-of-way over other aircraft in flight or operating on the surface

So it's the common sense meaning- an aircraft is in flight when it is flying and is not in flight when it is not.


text:
Is 40+ too old to start a Commercial Pilot career?
I'm 44 and I just started my private pilot journey, however I would like to see if is worth it to get the commercial and maybe fly for profit, I wonder how is the market for commercial airlines or maybe I would have better chances at smaller airliners or individual operations. I think CFI is one option

Try anyway. Make them tell you no.

The shortage of crews is real. Get an instructor rating and do that a few years, or go fly in the bush.  If you present yourself to a regional with 1500 hrs at age 50 or even 55, not a problem.  The problem is being able to live on the low pay.  If you're financially independent, go for it.

Will anybody hire you for bush flying with less than 1500 hours?

Consider carefully how long it will take to become and remain a competent CFI.

There are a lot of careers in aviation where you can fly an airplane and not be at an airline.  Airlines have an age restriction, these options do not.

Fly charter under Part 135.  Always get to fly to different places and fly some pretty sophisticated jets.  Some of the work is quite rewarding as you are transporting patients or transplant organs to help those in need.

Fly for a corporate flight department under Part 91.  Can fly to some unique locations and fly the same jets as charter companies do.  Quite a bit less regulations to follow under Part 91 vs Part 135.

Become a highly sought after CFI with specific specializations for an aircraft or avionics package, etc. in your area and make great money.

Become an examiner and ensure the next generation will operate the aircraft safetly and legally.

Work for the FAA and help ensure these companies are operating safely.

In what role do FAA agents fly aircraft?

@Bergi The two I'm most familiar with are R&D and Flight Check. You could ask a new question to get more.

At 44 and just started PPL your chance to go for Airline Pilot is very slim. You competitors are either 20 years younger or have 20 years worth of flight time plus Type Ratings under their belts. The reasons airlines prefer younger candidates are they are usually in a better health, they can work longer before retirement and they can offer lower salary to the youngs.
However besides Airline you can do other jobs with Commercial Pilot License. Banner towing and parachute planes come to my mind. If your area has nice scenery being a pilot for scenery tour is always an option.

I would assume it varies by location, but at least here in the U.S., don't most airlines have set pay schedules for X rank (FO/Captain) flying Y aircraft with Z years? So, the "can offer lower salary to the youngs" wouldn't be true in that case. Of course, it also means you'd be offered the same lower salary that other entry-level airline pilots are making.

@reirab pay scales often also take age and/or prior experience in other professions under account. As do the number of paid days off (which effectively does the same thing).

@jwenting Are you referring to the U.S.? Or elsewhere? I have not seen any age-based pay scales here (though, of course, ones based on years of experience are normal.) Also, what this answer suggests that companies would do - refusing to hire an older employee due to their age - is specifically illegal in the U.S. under federal labor anti-discrimination laws.

It's technically never too late to start a commercial career, I know people who quit and became instructors in their 40s, one in his 50s, and were happy they did it. One branched out and started flying charter and tour flights, another became an examiner, however none of them had any designs on flying for an airline. It's not impossible but it's pretty unlikely given the late start.
None of those jobs pay well. All of the people I know who went this way had paid off their mortgages and had some financial security, so they could afford to work for peanuts and go commercial for the love of it.
One alternative would be part time instructing, there are some very good instructors out there who have day jobs.

The people you refere to as becoming instructors: did they start ppl at ~40 and went straight to instructing?

All started as private pilots @Jpe61.

Yeppp, but the question is when. Time and experience are of essence when instructing others. I'd prefer not to be instructed by a person who's still wet behind the ears.

Start at forty, fly intensively and build up experience, you'll be a good instructor by fifty. Thing is you'll be competing younger instructors with similar experience, or instructors of similar age but thrice if not even more experience.

When it comes to instructing age isn't really that big a factor, you'll get paid the same. Most younger instructors are building up hours until they get their ATPL, so there's a lot of churn at flight schools, many would be happy to have a good instructor who is likely to stick around.

I agree as long as the young instructors are on ATPL track, which I do not think would be the case in this particular situation. I've have first hand experience of both young and the seasoned kind, and only negative experience has been an instructor not on ATPL track. Having said that I gained the most information and knowlege from ex military pilots. They know their s_ _t.

I didn’t earn my PPL and instrument until 34. I flew around for years just enjoying the pleasure of flight. Two decades later, at 56 I added CPL/CFI. I now work as a part time instructor and can tell you without reservation, it is the greatest gig!
Helping other people achieve their dreams is an incredible privilege.


text:
calculating TH,TC,MH,MC,CH,CC
TC: 032°; WCA: +11°; DEV: 001° W; CH: 049°
What are TH, VAR und MH?
a) TH: 048°.
VAR: 005° E.
MH: 050°.
b) TH: 043°.
VAR: 005° W.
MH: 048°.
c) TH: 043°.
VAR: 005° E.
MH: 048°.
d) TH: 048°.
VAR: 005° W.
MH: 043°.

regard this question, I have a big confusion answering this kind of questions .. i would be happy for a good explanation regarding it .
I know that :
TH = TC + WCA
VAR = TH - MH
DEV = MH - CH

in regard of the question , TH is : 32 + 11 WCA = 43.
to find the MH i can use the deviation equation .
DEV 1 = x(MH) - 049(CH) = x = 50
now to get the VAR 43 - 50 = -7 VAR
this is were i got stuck which of course doesn't make sense ..

TC ± WCA = TH ± VAR = MH ± DEV = CH

Let's take this one step at a time.
TC: 032°; WCA: +11°; DEV: 001° W; CH: 049°
What are TH, VAR und MH?

TC ± WCA = TH     032° + 11° = 043°.

CH ± DEV = MH     049° - +1 = 048°  (formula rearranged)

VAR = MH - TH     048° - 043° = 5°  (formula rearranged)
(positive values are westerly and negative values are easterly)

thank you very much for the detailed explanation , much appreciated


text:
When does the wing anti-ice valves open after take-off on the A320?
I know that if wing anti-ice is used on ground on the A320 the wing anti-ice valves will open for a period of 30seconds for a self test and then close as long as aircraft is on ground.
So my question is if wing anti-ice is kept ON when will the anti-ice valves open?
After lift off or in some other flight phase?

Well the heat has to be on for takeoff, so at minimum, it's going to be when thrust rises above some threshold with the system turned on.

The wing anti-ice valves are controlled by the state of the push-button, a timer and the ground/flight sensor:

Source: A320 FCOM, Ice and rain protection section.

If the panel push-button is switched ON on the ground, the valves open and are closed after 30s by a timer.

When in flight, the valves are open as long as the panel push-button is ON.

If the push-button is set to ON on the ground and left in this state, the 30s test is conducted, the valves close and only reopen when the sensor indicates the aircraft has left the ground. The valves then remain open until the push-button is set of OFF.
The bleed monitoring computer (BMC) may override this logic if required.

So the system lets you take off with the LEs cold even if the system is selected on?

@JohnK Ice protection on the ground is provided by anti-icing fluids. WAI cannot be used on the ground due to potential for overheating and structural damage. Same situation with 777 and the E-Jets.

On the CRJ200 you must have the system on and the LEs hot for takeoff (and by hot, I mean they are heated to above 100C, as an "evaporative" WAI system) for a TO in icing. WAI on takeoffs have a performance allowance in the QRH. Slats provide a lot more leeway I suspect, because they make the wing way less sensitive to contam. The 200's hard LE can tolerate very little LE roughness.


text:
What’s the grass parts between runways and taxiways called? And is there a regulation for this unpaved surfaces on FAA?
I wasn’t able to find any regualtions for unpaved surfaces on FAA. When I search for unpaved surfaces all I’m seeing are regulations for unpaved runways. But what I’m looking for is the regulations for unpaved soil or grass parts of a paved runway.

Yeah I'm looking if we can use gravel or stone instead of grass and we can use stone what the diameter should be?

There is not one regulation for all unpaved areas of an airport and there are multiple unpaved areas that are part of a paved runway. A shoulder immediately surrounds the paved area. This area may be used by emergency or snow clearing vehicles as needed.

Surrounding this is the Runway Safety Area, which is to be graded according to regulation.

The RSA is a defined surface surrounding the runway, typically 500-feet wide and extending 1,000-feet beyond each runway end. It provides a graded area in the event that an aircraft overruns, undershoots or veers off the side of the runway (runway excursion).
ref

Surrounding this is the Runway Object Free Area, which is unsurprisingly to be free of obstacles.

ROFA is a clear area limited to equipment necessary for air and ground navigation, and provides wingtip protection in the event of an aircraft excursion from the runway.

This diagram also shows the Runway Protection Zone which is part of the runway but is not immediately adjacent to a runway.
AC 150/5300-13B contains airport design specifications and has details of requirements for these areas.

Thank you for your answeri it was really helpful. I didn't really see which materials we can use for runway safety area surface. I've seen they use stone for paved and unpaved surfaces transition. Can they be using it for shoulder purposes?

The areas in question are called "islands".
The FAA Adisory Circular - Airport Design (link to pdf) defines the island as

1.5 Definitions.
...

Island. A non-serviceable paved or grassy area bounded by a taxiway, taxilane, or
apron pavement.

The FAA advisory circular - Standards for airport markings (link to pdf), defines the island as:

1.2. Definitions.
The following definitions apply to terms used in this AC.
...
d. Island. An unused paved or grassy area between taxiways, between runways, or
between a taxiway and a runway. Paved islands are clearly marked as unusable, either by
painting or the use of artificial turf. For the purposes of this AC, islands are also referred to as
“NO-TAXI” islands.

The grass covered parts of airports (amongst pretty much everything else) is discussed at great length in FAA Advisory Circular -  Standard Specifications for
Construction of Airports, the grass is referenced as "turf" in the document.

Thank you for your answer.

@ayiyogi please do not hesitate to give points to all answers that help


text:
What type of materials can be used for runway shoulders?
Instead of paving the shoulders what are the easier solution can be usedwithin FAA regualtions?

They sometimes put fake grass or polyethene sheets. I do not know about the regulations regarding this though. There was one video where a 747 on takeoff was blowing off the side fake grass sheets probably due to bad installation

See in 6.3 - Shoulder Material Requirements in AC-150/5320


text:
What types of surface materials can be used for the transition between paved and unpaved surfaces on a runway?
I wasn't able to find much about it on FAA. Can anyone guide me? I've seen some airports using gravel but isn't it dangerous for aircraft? how can they elliminate the FOD danger?


text:
Would it be practical to have missiles that can aim forward and backwards?
I have been researching recent air-to-air combat kills in some recent wars and in every case it seemed that the pilot who was in the back won. So I was wondering why they don't just design a missile capable of swiveling around and targeting a bogey behind the aircraft. I understand there are some physic issues with it but surely it wouldn't take long for physicists and engineers to come up with a solution

but surely it wouldn't take long for physicists and engineers to come up with a solution: it is a common misconceptions. Engineering is about finding trade-off: you can have many things, but you should sacrifice a lot more things. Really: real world is much more complex and we cannot have everything.

Imagine the drag of that missile when it's 90° to the chasees current direction of travel. Holy drag & vibration, Batman!!

As an alternative, one could have one missile permanently mounted for reward firing with a missile specifically designed & shrouded for reverse flight. Of course, you're then wasting a launch rail, fuel, range, speed & maneuverability for something that might be used in <1% of encounters and only in a situation that you're explicitly trained to not allow to happen. (It does happen, of course, but you're not supposed to allow the bogey to get behind you.)

I was under the impression that most newer missiles can attack targets all around the aircraft. The IRIS-T (developed 2001) can attack targets 360° around the airplane, at least when mounted on the Eurofighter Typhoon. (But I believe not when mounted on the F-16 because it lacks the necessary sensor integration.) That's a 20+ year old missile and it already has the feature you ask for. Same for the AIM-9X Block II (2010s).

Well, you could have a missile inside a missile.  The outer missile would be designed to fire backwards off the launch rail.  The big fins would be in the front of the missile, and the little fins (if any) would be in the back.   Once the outer missile has accelerated to zero airspeed, the inner missile fires out of it.  The inner missile breaks out through the frangible nose cone of the outer missile, the folding fins unfold, and there you go.

(Or simpler, just have a missile pointing rearward on the launch rail, with an extra set of large fins at the nose of the missile, that get jettisoned once the missile has accelerated to zero airspeed.)

So I was wondering why they don't just design a missile capable of swiveling around and targeting a bogey behind the aircraft.

They did. The AIM-9X is able of doing precisely that.
The caveat is, you're looking at much lower kill probability (Pk).
Studies indicate short-range IR-guided missiles to have a Pk as high as 74% when launched normally, at a visually acquired aircraft in front.
Doing a 180 turn exposes the missile to the same kill-chain failures that BVR (Beyond-Visual-Range) missiles normally face. Missile seekers have a narrow field of vision, and there's little time to search. Unless the missile happens to catch the target just right when it turns, it's going to fly past. This brings expected Pk to the same 10%-25% range as BVR missiles in challenging conditions. That's not enough when you're only carrying two short-range missiles.
Lock-on-after-launch capability was initially introduced for internal storage on stealth aircraft, and only later adapted for a possible backward engagement. It's necessary for any stealth aircraft, but most missiles aren't designed to do a full 180.
The AIM-9X is not the only one. As always, there's few military ideas imaginable that the Soviets haven't tried at some point. They have apparently decided it's not worth pursuing, but apparently they had at least a concept for a rear-firing missile. There were similar ideas in the US as well. We're rapidly entering speculation here however.
Out of related concepts, the Flanker comes with a rear-facing radar. The new Su-57 has both front- and rear-facing laser turrets to blind attacking IR-guided missiles. But no rear-facing missiles. Instead, the idea for it is to use the very risky Cobra Maneuver to trade places with the pursuer.

Your link says the Cobra maneuver is used for dogfights, which means no missiles.

@AnonymousPhysicist - "is used for dogfights" might actually be "has never been used in actual combat".

@AnonymousPhysicist Short-range missiles are used in dogfights.

@AnonymousPhysicist In no way does “dogfight” imply guns only.

"The AIM-9X is not the only one." – The German IRIS-T, for example, can attack targets behind the aircraft, at least when fired from an Eurofighter Typhoon. The missile can also be used on F/A-18, F-16, Gripen, and Tornado, but at least for the F-16, it cannot use its full potential, including 360° targeting, due to lack of sensor integration.

Typical missiles have fins in the back that are used for steering.  If the missile is launched towards the rear of the aircraft, it will have a tail wind.  Then the fins will be destabilizing instead of stabilizing.  The missile will quickly become a bunch of missile parts.
It would be possible to design an air launched missile that did not have this problem.  In practice, ground launched missiles work fine.

Actually, many/most air to air missiles have the steering fins at the front. AIM-9 and AIM-120, for example. Not that it makes a real difference, though.

Which fins are static and which steer indeed doesn't matter.  You're firing an arrow backwards, and the few moments it spends at "negative airspeed," while trying to reach designed airspeed, are enough to make it tumble, possibly into your own airplane.  Recall the test pilot who lived to tell the tale of shooting himself down.

@WPNSGuy Where are the fins at the front of this AIM-120? https://media.defense.gov/2003/Mar/28/2000031135/-1/-1/0/030328-F-JZ000-019.JPG

Static fins at the rear are a very important part of the steering system.

@AnonymousPhysicist - Frontish. On the -120, more to the middle. The fins at the rear are static, and do not steer/swivel. Maybe I should have said "towards the front", instead of "at the front"

That is a whole lot of machinery to design a swivel missile launcher rail. Things that can fail.
Then, a different missile to be launched at a starting speed of 'minus 500 mph" or so. Backwards.
If the enemy is behind you, you've already lost. In the time it takes you to rotate that launcher...his missile is already in the air, chasing your tailpipe.
Another thing you're probably missing is that air to air combat is rarely 1 v 1. There is almost always a wingman.

Swing-wing aircraft do have launcher rails that pivot, so it can be done. Probably not particularly efficiently, though. Of course, swing wing aircraft don't have the wings go through 180° of rotation.

@FreeMan - Yes, but differently pivot. In a former life, I was a WPNS guy on F-111E. Much experience with the pivot pylons. Major PITA. I can only imagine the maintenance nightmare with a wingtip rotatable launcher. Is it possible to design and build? Sure. But since we've not seen one yet, no one has thought it worth the effort.

Oh, I agree 100% Anything is possible, but practical, economical, real-world feasible? Not so much

I'm virtually certain that this concept has been brought up many times in the history of combat aircraft. And the senior members of the design team said "Yeah, we looked at that 20 years ago. It was a bad idea then, it is a bad idea now."

The M2 Browning certainly does not have a problem firing forwards or backwards owing to its Mach 2.5+ muzzle velocity.
A rearward fired missile could theoretically be propelled away from the aircraft fast enough to gain net positive forward velocity.
Rocket augmented artillery shells are already in existence, potentially increasing the M2's already impressive 2000 yard effective firing range.
One might wonder if an updated version of the B-29 computer fire control system with upgraded shells and a ball turret could do  against an upcoming Stinger missile.